The multiverse theory really complements time travel. This is done by creating a situation where you can not encounter a paradox. The individual that is time traveling is just merely going to a separate time line where that event occurs. This way you can go back kill your grandfather and come away scot free. The multiverse theory is supported by quantum physicists, and is the best way for describing backwards time travel. While the theory of relativity still is the best example of forward time dilation. This theory makes it possible to do away with all the contradictions to time travel.